public class OverwritePeRequestNew
{
    public String Prefix = PESampleRequest__c.sObjectType.getDescribe().getKeyPrefix();  
    
    public OverwritePeRequestNew(ApexPages.StandardController controller){
        this.controller=controller;
        
    }
    private final ApexPages.StandardController controller;
    
    public PageReference Cancel()
    {
        PageReference pr=new PageReference('/'+Prefix );
        pr.setRedirect(true);
        return pr;
    }    



}